JPH07113077B2 - Improved ester curing agent for phenolic resin binder systems - Google Patents

Description

FIELD OF THE INVENTION The present invention relates to an alkaline phenolic resin binder system that is cured by an ester curative, a moldable composition comprising the binder and agglomerate material, and a moldable from the binder. A method of making a composition. More specifically,
The present invention relates to foundry binder compositions, moldable compositions comprising the compositions and agglomerate materials, and foundry cores or molds made from the compositions and methods of making the same.

BACKGROUND OF THE INVENTION Binders or binder systems intended for use in foundry cores and molds are well known. In casting technology,
Cores or molds for making metal castings are usually prepared from agglomerate material such as sand, and a binding amount of a binder or mixture of binder systems. Typically, after mixing the agglomerate material and binder, the product mixture is pushed in,
It is blown or otherwise shaped into the desired shape or mold and then cured using a catalyst and / or heat to a solid, cured state.

Resin binders used in the manufacture of foundry molds and cores are often cured at elevated temperatures to achieve the fast-hardening cycle required in foundries. However, in recent years, resin binders that cure at low temperatures have been developed. This method is preferred over high temperature cure methods which have high energy requirements and which often cause undesirable fume generation.

Certain methods that do not require heating to cure the resin binder are referred to as non-baking methods. In this method, a binder component is coated on the surface of the agglomerate material, such as sand, and the resulting mixture is pressed, blown or otherwise shaped into the desired shape or mold. Curing of the binder takes place without heating.

One of the non-baking methods uses an alkaline aqueous solution of phenolic resole resin as a binder. In this method, usually the molding sand is mixed with the ester hardener and then the resole resin solution is added to the mixture. This method is described in U.S. Pat.
It is described in detail in No. 4,904 (Re No. 32.812).

The ester cure method outperforms some conventional methods from an environmental standpoint. However, the initial tensile strength of cores made by this method tends to be somewhat lower than those made by other baking methods.

In Japanese Patent Application Laid-Open No. 62-282743, the absolute amount of the binder added is increased to obtain an ester-cured resin having high tensile strength. This was accomplished using an organic ester solution of phenol formaldehyde resin as the curing agent. Examples of ester solutions of resole resins as well as novolac resins have been presented. However, this method has limitations. The novolac resin used is only soluble in gamma-butyrolactone and is insoluble in other ester curing agents useful in many applications of alkaline phenolic resin binders. The disclosed resole resins do not form stable solutions in many ester hardeners.

The present inventors have discovered that an ester solvent solution of a benzyl etherified phenol resin resole resin is an excellent curing agent for use in the ester curing method. High initial tensile strength cores made using this binder system are achieved without increasing the absolute amount of binder added. In addition, benzyl ether phenolic resins form stable solutions in triacetin (glycerol triacetate), ethylene glycol diacetate and other ester hardeners where conventional resole resins are not stable.

SUMMARY OF THE INVENTION In accordance with the present invention, a curing agent for an alkaline phenolic resin-based resole resin binder comprising an ester solution of a benzyl ether resole resin, wherein the benzyl etherified resole resin comprises from about 5% to about 40% by weight of the solution. A composition is provided.

Further, according to the present invention, an alkaline aqueous solution of a phenol resin-based resole resin and a curing agent for the phenol resin-based resole resin are used, the curing agent is an ester solution of a benzyl etherified resole resin, and the benzyl etherified resole resin is A binder composition is provided that comprises from about 5% to about 40% by weight of the curing agent.

Further, according to the present invention, a casting molding composition comprising a mixture of a particulate refractory material such as sand and the binder composition of the present invention, and a casting core and a mold using the casting molding composition. A manufacturing method is provided.

DETAILED DESCRIPTION OF THE INVENTION The benzyl ether resole resin used in the practice of the present invention is capable of reacting with phenols and 1
Prepared by reaction with a molar excess of aldehyde. Methods for preparing the resin are well known and are described, for example, in U.S. Pat.
No. 797. The phenols used to make the phenolic resin can be any of the monohydric phenols commonly used to prepare phenolic resins. Typical phenol numbers include phenol itself and cresols. A particularly useful phenol is orthocresol. U.S. Pat.No. 4,246,157
The publication describes in detail the preparation of a benzyl ether resole resin from a commercially available 80% orthocresol.

The aldehydes used to form the benzyl etherified resole resin can also be quite extensive. Suitable aldehydes include formaldehyde, acetaldehyde, propionaldehyde, furfuraldehyde, and any of the aldehydes previously used to form phenolic resin-based resole resins such as benzaldehyde. Generally, the aldehyde used is of the formula RCHO (wherein R
Is hydrogen or a hydrocarbon group having 1 to 8 hydrogen atoms). The most preferred aldehyde is formaldehyde.

The molar ratio of aldehyde to phenols used to make the benzyl etherified resole resin of the present invention is about 1.1:
1 to 2.5: 1. Desirably, the molar ratio of aldehyde to phenols is in the range of about 1.2: 1 to about 2.2: 1.

Alkoxy modified benzyl etherified resole resins are particularly useful in the method of the present invention. Methods for preparing the compounds are well known and are described, for example, in U.S. Patents 4,546,124 and 4,6.
No. 57,950. These resins are prepared by etherifying at least some of the methylol groups of the resin with lower aliphatic alcohols having 1 to about 4 carbon atoms. The resin has an alkoxymethylene group attached to the benzene ring. Said group formula - (CH ₂ O) _n R
(Wherein R is an alkyl group of the alcohol used and n is a small positive integer). This group is a substituent in the ortho or para position with respect to the phenolic hydroxyl group in the resin.

The ester used to prepare the hardener composition of the present invention can be an ester normally used to cure alkaline phenolic resin-based resole resins.
The ester includes gamma butyrolactone, triacetin,
Examples include ethylene glycol diacetate, propylene glycol diacetate, propylene carbonate, dimethyl succinate, dimethyl adipate, dimethyl glutarate, glycerol mono- and diacetate.
Mixtures of these esters can also be used.

As mentioned above, the hardener composition of the present invention comprises an ester solution of a benzyl etherified resole resin. The resole resin comprises about 5 to about 40% by weight of the solution, preferably about 15 to about 30% by weight.

The curing agent of the present invention is used to cure an alkaline solution of a phenolic resin-based resole resin binder. The binder has a molar ratio of alkali to phenols in the range of about 0.2: 1 to about 1.2: 1. The preferred alkali to phenol molar range is from about 0.4: 1 to about 0.9: 1. The alkali used in the resin is usually KOH, NaOH, or mixtures thereof, but other alkalis are not excluded. The resin binder solution is preferably an aqueous solution having a solids content in the range of about 40 to about 75% by weight.

Binders using the hardeners of the present invention are useful in preparing foundry compositions. The composition comprises a particulate refractory material and an aqueous alkaline binder solution of from about 0.5 to about 8% by weight of the refractory material. The particulate refractory material used in the molding composition can be a refractory material used in the casting industry to make molds and cores, such as silica sand, chromite sand, zircon sand or olivine sand and mixtures thereof. When using such sand, it is desirable that the binder solution be present in an amount of about 1 to about 3% by weight of the sand.

Other commonly used additives such as urea and organosilanes can optionally be used in the binder composition of the present invention. Organosilanes, known as coupling agents, enhance the adhesion between the binder and sand. Examples of useful coupling agents of this type are aminosilanes, epoxysilanes, mercaptosilanes, hydroxysilanes, and ureidosilanes.

When the binder of the present invention is used to make foundry cores and molds, a refractory material such as foundry sand is thoroughly mixed with an ester hardener containing a benzyl etherified resole resin. The alkaline phenolic resin-based resole resin binder solution is then added to this mixture. Mixing is performed until substantially all sand particles are completely and uniformly coated with the binder solution. Alternatively, the resin binder solution can be first mixed with sand and then the ester curing agent can be added to the mixture, or the binder solution and the ester curing agent can be added simultaneously. In either case, the binder and hardener coated refractory material is then placed in a core or mold box. The mixture is cured at ambient temperature.

The following specific examples illustrate the invention. The examples are not intended to limit the invention in any way. All parts and percentages are by weight unless otherwise noted.

Example I A benzyl etherified resole resin was prepared by mixing 34.21 parts of 80% orthocresol and 9.09 parts of phenol in a flask equipped with a stirrer and condenser. Then 50%
Formaldehyde solution 32.0 parts, 25% zinc acetate aqueous solution 2.07
Parts and 0.177 parts of CaO were added. The contents were heated under reflux with stirring until the free formaldehyde content in the solution was less than 3% by weight. Further 50% citric acid aqueous solution
After adding 0.354 part, water was removed under vacuum. The mixture was then heated at 90 ° C. for about 2 hours and then cooled. An ester curing agent solution was prepared by dissolving 20 parts of the resin in 80 parts of gamma-butyrolactone.

The binder phenolic resin was prepared as follows. That is, 610 g of phenol, 820 g of 50% formaldehyde and
A mixture of 44g of 55% KOH solution and a solution viscosity of 430-470 at 25 ℃.
Heated under reflux until cps. The mixture was cooled to room temperature and 500 g of 55% KOH solution was added. Finally, 0.39% by weight of gamma aminopropyltriethoxysilane was added to the resin and mixed well. The viscosity of the produced resin is 155 cps at 25 °
Thus, the formaldehyde to phenol molar ratio was 2: 1 and the KOH: phenol ratio was 0.82: 1.

A test core was prepared by the following method. That is, about 2.5k
To an amount of g of washed and dried silica sand was added 1.44% phenolic resin binder solution and the mixture was stirred in a Hobart Kitchen Aid mixer for 1 minute. Then, a gamma-butyrolactone solution of a benzyl etherified resole resin-containing ester curing agent was added at 31.1% by weight of the resin. The mixture was stirred for an additional 30 seconds and then used immediately in a Dietert 696 core box to the standard American Foundrymen Society.
1 inch dog bone tensile test pieces were molded. The cores were cured at room temperature and the samples broke at various time intervals after formulation.
Tensile strength is measured by measuring the tensile strength of the core.
Strength accessory) Dietert Univer with 610-N attached
It was performed using sal Sand Strength Machine 400-1. Three
The average value of the tensile strength measurements made 4 to 4 times was recorded.

The contrast test was conducted with 1.5% resin to sand and 25% by weight gammabutyrolactone curing agent of the resin. These ratios are used so that the amount of resin used in the above test and the total amount of the same resin on the sand are the same. From the test results shown in Table 1, cores made with the ester hardener composition of the present invention exhibit much higher initial tensile strength than cores made with the usual hardener, gamma-butyrolactone. I understand.

Example II A methoxy-modified benzyl etherified resin was prepared by the following method. That is, a mixture of 38.31 parts phenol, 39.61 parts formaldehyde, 10.87 parts methanol and 3.2 parts 25% aqueous zinc acetate solution was stirred under reflux until the free formaldehyde content was less than 3%. Further 0.4 parts citric acid was added and the mixture was vacuum dried. The temperature was then raised and the mixture held at 90 ° C for 1 hour. 20 parts of resin were mixed with 80 parts of gamma butyrolactone to make an ester hardener solution. Using the same method and proportions used in Example I, this hardener solution was used to cure sand cores coated with phenolic resole resin.

The test cores prepared in this way are 1, 2 and 2 after preparation.
After 4 hours it showed average tensile strengths of 120 psi, 140 psi and 167 psi. These test results demonstrate the excellent tensile strength of cores made with a curing agent containing an alkoxy modified benzyl etherified resole resin.

Example III A benzyl etherified resole resin was prepared from unsubstituted phenol as follows. That is, phenol 1100g, 5
A mixture of 950 g of 0% aqueous formaldehyde and 58.7 g of 25% aqueous zinc acetate was heated under reflux with stirring until the free formaldehyde content in the solution was less than 3%. Then 10 g of 50% aqueous citric acid was added and the mixture was mixed with 5 g.
It was cooled to 0 ° C. and dehydrated under vacuum. The mixture is then placed under vacuum 9
Heated at 2 ° C. for 2 hours.

Using the same method and proportions used in Example I, a solution of 20 parts of resin in 80 parts of gammabutyrolactone was used to cure a sand core coated with a phenolic resin-based resole resin. The test cores thus prepared were 125 psi, 136 psi, 174 psi and 18 psi after 1, 2, 4 and 24 hours, respectively.
It showed an average tensile strength of 4 psi. This shows the excellent tensile strength of the core made again using the benzyl etherified resole resin-containing curing agent.

Example IV A comparison test was conducted using the improved ester curing agent disclosed in Japanese Patent Application Laid-Open No. 62-282743. The hardener contained a phenolic resin prepared as follows. That is, a mixture of 767 g of phenol, 50 g of a 41.5% aqueous formaldehyde solution and 4.1 g of oxalic acid was heated to 85 ° C. with stirring, and while the mixture was refluxed, a 41.5% aqueous formaldehyde solution was gradually added over 30 minutes. The mixture was refluxed for another 2 hours with stirring and then the mixture was dehydrated by heating under vacuum to a temperature of 150 ° C. A curing agent was prepared by dissolving 35 parts of the cooled resin in 65 parts of gamma-butyrolactone.

An alkaline solution of a phenol resin-based resole resin was prepared according to the disclosure of Japanese Patent Application Publication. This is 168g phenol, 323g 41.5% aqueous formaldehyde solution and 48%
A reaction of 209 g of aqueous KOH solution at 85 ° C. for 5 hours was required.
The solution was dehydrated to a water content of 45.6% to obtain a resin solution having a viscosity of 122 cps at 25 ° C. To this solution was added 0.4 wt% gamma aminopropyltriethoxysilane. Sandy
A test sand core was prepared according to the general procedure set forth in Example I using 1.38 wt% resin and 38.2 wt% resin hardener solution.

1.38 wt% phenolic resin and 38.2 wt% of resin
Benzyl etherified resole resin as described in Example I of
The test was repeated with sand coated with a hardener containing 35% and 65% gamma-butyrolactone. From the test results shown in Table 2, the curing agent containing the benzyl etherified resole resin of the present invention has a tensile strength significantly higher than that of the core made using the improved curing agent described in Japanese Patent Application Laid-Open No. 62-282743. It can be seen that it produces a core with strength.

A similar test was conducted in which the ester hardener was a mixture of 20 parts resin, 20 parts gamma butyrolactone and 60 parts triacetin. The test results shown in Table 2 also show the superiority of the ester curing agent containing the benzyl etherified resin.

Example V The benzyl etherified resole resins of Examples I and III were dissolved in ester triacetin to give another example of an ester curing agent. This hardener solution contained 20% benzyl etherified resin. The alkaline solution of phenolic resin binder contained a higher proportion of KOH: phenol than that used in Example I. This was prepared by mixing 95.6 parts of the resin binder of Example I with 4.4 parts of a 60% KOH solution.

A sand core coated with 1.44% by weight of this resin and 31.1% by weight, based on the resin weight, of the triacetin hardener containing the benzyl etherified resin of Examples I and III was prepared. The contrast test was performed with 1.5% by weight of a phenolic resin binder over the sand and 25% by weight of the resin triacetin hardener alone. The test results shown in Table 3 show that the sand cores prepared using the alkaline phenolic resin-based resole binder cured with the curing agent of the present invention were cured with the usual ester curing agent, triacetin. It shows that it has excellent tensile strength.

Therefore, it is apparent that the present invention provides an improved ester curing agent for an alkaline phenolic resin-based resole resin binder system and a binder composition for castings containing the curing agent, which sufficiently satisfies the above objects, goals and advantages. Is. Although the present invention has been described in relation to particular embodiments, it will be apparent that many alternatives, modifications and variations will be apparent to those skilled in the art in view of the above description.
Accordingly, it is intended to include all alternatives, modifications and variations as manifested within the spirit and broad scope of the appended claims.

The embodiments of the present invention are as follows.

1. comprising a solution of benzyl ether resole resin in an ester, wherein the benzyl ether resole resin is about 5% of the solution.
A curing agent composition for an alkaline phenolic resole resin binder, which accounts for 1 to 40% by weight.

2. The curing agent composition according to 1 above, wherein the phenols used in the preparation of the benzyl ether resole resin are selected from the group consisting of phenol, orthocresol and mixtures thereof.

3. The curing agent according to 1 above, wherein the benzyl ether resole resin is an alkoxy-modified benzyl ether resole resin.

4. The benzyl ether resole resin as described in 3 above, wherein the alkoxy modified benzyl ether resole resin is a methoxy modified benzyl ether resole resin.

5. The curing agent composition according to 1 above, wherein the ester is selected from the group consisting of gamma butyrolactone, triacetin, and mixtures thereof.

6. About 15 to about benzyl ether resole solution
The curing agent composition according to 1 above, which accounts for 30% by weight.

7. An alkaline aqueous solution of a phenolic resole resin and a curing agent for the phenolic resole resin, the curing agent comprising a solution of a benzyl ether resole resin in an ester, the benzyl ether resole resin being about 5 to Binder composition comprising about 40% by weight.

8. The binder composition according to the above 7, wherein the phenols used for preparing the benzyl ether resole resin are selected from the group consisting of phenol, orthocresol, and a mixture thereof.

9. The binder composition according to the above 7, wherein the benzyl ether resole resin is an alkoxy-modified benzyl ether resole resin.

10. The binder composition according to 9 above, wherein the alkoxy-modified phenol resin-based benzyl ether resole resin is a methoxy-modified benzyl etherified resole resin.

11. Esters are gamma butyrolactone, triacetin,
The binder composition according to 7 above, which is selected from the group consisting of: and a mixture thereof.

12. The binder composition according to 7 above, further comprising silane.

13. The binder composition of claim 7 wherein the benzyl ether resole resin comprises about 15 to about 30% by weight of the curing agent.

14. A foundry composition comprising a particulate refractory material such as sand and a binder composition as described in 7 above.

15. The casting molding composition according to 14 above, wherein the phenols used for preparing the benzyl ether resole resin are selected from the group consisting of phenol, orthocresol, and a mixture thereof.

16. The casting molding composition as described in 14 above, wherein the benzyl ether resole resin is an alkoxy-modified benzyl etherified resole resin.

17. The above wherein the alkoxy-modified benzyl ether resole resin is a methoxy-modified benzyl etherified resole resin
16. The composition for casting molding according to 16.

18. Esters are gamma butyrolactone, triacetin,
15. The casting molding composition as described in 14 above, which is selected from the group consisting of: and a mixture thereof.

19. The foundry composition of claim 14 wherein the binder composition comprises from about 0.5 to about 8% by weight of the composition.

20. The casting molding composition as described in 14 above, wherein the binder composition further contains silane.

21. The casting molding composition according to 14 above, wherein the benzyl etherified resole resin accounts for about 15 to about 30% by weight of the curing agent.

22. A granular refractory material is mixed with an alkaline aqueous solution of a phenolic resole resin and the curing agent composition described in 1 above, and the mixture is mixed with a core box or a mold (pattern mol).
A method for producing a casting core and a mold, which comprises placing the resin in d) and curing the resin.

23. The alkaline aqueous solution of phenolic resin-based resole resin is about 0.5 to about 8% by weight of the particulate refractory material.
2 Method described.

24. The method according to 22 above, wherein the binder composition further comprises silane.

Claims (7)

[Claims] 1. A curing agent composition for an alkaline phenolic resole resin binder comprising a solution of benzyl ether resole resin in an ester, said benzyl ether resole resin comprising about 5 to about 40% by weight of said solution. 2. An alkaline aqueous solution of a phenolic resole resin and a curing agent for the phenolic resole resin, the curing agent comprising a solution of a benzyl ether resole resin in an ester, the benzyl ether resole resin being a curing agent. A binder composition comprising from about 5 to about 40% by weight. 3. The binder composition according to claim 2, further comprising silane. 4. A particulate refractory material such as sand and claim 2.
A casting molding composition comprising the binder composition described. 5. The molding composition according to claim 4, wherein the binder composition further contains silane. 6. A particulate refractory material is mixed with an alkaline aqueous solution of a phenolic resole resin and the hardener composition of claim 1 and the mixture is used as a core box or patt.
ern mold) and curing the resin. 7. The method of claim 6 including a binder composition and further a silane.